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Wednesday, 28 December 2011

I am sorry for not posting anything lately. I would like to wish everyone a belated Merry Christmas and a Happy New Year. I will be posting new articles after the New Year. Meanwhile, please follow my activity on Twitter and facebook. Thank you very much for your support.

Monday, 19 December 2011

The ice-like hexagonal structure of
water molecules interacting with and above a model platinum catalyst
surface is determined from quantum chemical calculations. Oxygen atoms
in water shown as red, hydrogen atoms as white; platinum atoms are shown
in bluish-grey. High-level details of the structure can be seen in the
reflections of each atom surface. Rees Rankin (Argonne's Center
for Nanoscale Materials) Photo courtesy of Argonne National Laboratory.

Catalysts are all around us.

Catalysts are one of those things that few people think much about, beyond perhaps in high school chemistry, but they make the world tick. Almost everything in your daily life depends on catalysts: cars, Post-It notes, laundry detergent, beer. All the parts of your sandwich—bread, cheddar cheese, roast turkey. Catalysts break down paper pulp to produce the smooth paper in your magazine. They clean your contact lenses every night. They turn milk into yogurt and petroleum into plastic milk jugs, CDs and bicycle helmets.

What is catalysis?

Catalysts speed up a chemical reaction by lowering the amount of energy you need to get one going. Catalysis is the backbone of many industrial processes, which use chemical reactions to turn raw materials into useful products. Catalysts are integral in making plastics and many other manufactured items.

Even the human body runs on catalysts. Many proteins in your body are actually catalysts called enzymes, which do everything from creating signals that move your limbs to helping digest your food. They are truly a fundamental part of life.

Small things can have big results.

In most cases, you need just a tiny amount of a catalyst to make a difference. Even the size of the catalyst particle can change the way a reaction runs. Last year, an Argonne team including materials scientist Larry Curtiss found that one silver catalyst is better at its task when it's in nanoparticles just a few atoms wide. (The catalyst turns propylene into propylene oxides, which is the first step in making antifreeze and other products.)

It can make things greener.

Industrial manufacturing processes for plastic and other essential items often produce nasty by-products which can pose hazards to human health and the environment. Better catalysts can help solve that problem. For example, the same silver catalyst actually produces fewer toxic by-products—making the whole reaction more environmentally friendly.

At its heart, a catalyst is a way to save energy. And applying catalysts on a grand scale could save the world a lot of energy. Three percent of all of the energy used in the U.S. every year goes into converting ethane and propane into alkenes, which are used to make plastics, among other things. That's the equivalent of more than 500 million barrels of gasoline.

Catalysts are also the key to unlocking biofuels. All biomass—corn, switchgrass, trees—contains a tough compound called cellulose, which has to be broken down to make fuel. Finding the perfect catalyst to disintegrate cellulose would make biofuels cheaper and more viable as a renewable energy source.

Often, we have no idea why they work.

The precise reasons why catalysts work are often still a mystery to scientists. Curtiss works in computational catalysis: using computers to tackle the complicated interplay of physics, chemistry and math that explains how a catalyst operates.

Once they've figured out the process, scientists can try to build a catalyst that works even better by simulating how different materials might work instead. Potential configurations for new catalysts can run to thousands of combinations, which is why supercomputers are best at dealing with them.

When Edison was building the lightbulb, he tested literally hundreds of different filaments (likely testing the patience of his lab assistants as well) before discovering the carbonized filament. By taking advantage of supercomputers and modern technology, scientists can speed up the years of testing and expense to get to breakthroughs.

Curtiss runs simulations on Argonne's Blue Gene/P supercomputer to design possible new catalysts. "As supercomputers have gotten faster, we've been able to do things we'd never have been able to do 10 years ago," he said. They could be essential for the next big revolution in batteries.

Newly efficient lithium-ion batteries helped turn clunky car phones into the slim, elegant cell phones and laptops available today. But scientists are already searching for the next revolution in batteries—one that could someday make a battery light and powerful enough to take a car 500 miles at a go. A promising idea is lithium-air batteries, which use oxygen from the air as a primary component. But this new battery will require totally revamping the internal chemistry, and it will need a powerful new catalyst to make it work. A lithium-air battery works by combining lithium and oxygen atoms and then breaking them apart, over and over. That is a situation tailor-made for a catalyst, and a good one would make the reaction faster and make the battery more efficient.

How do you make a new catalyst?

Understanding the chemistry behind reactions is the first step; then scientists can use modeling to design potential new catalysts and have them tested in the lab. But that first step is difficult unless you can get down to the atomic level to see what is happening during a reaction. This is where big scientific facilities like Argonne's Advanced Photon Source (APS) shine. At the APS, scientists can use the brightest X-rays in the United States to track the reactions in real time. At the laboratory's Electron Microscopy Center, researchers take photos of the atoms while they react. Curtiss and the team have used both of these in their search for better catalysts.

Our posting of UTC Power’s February 2011 infographic comparing the energy conversion and green tech attributes of their 400 kilowatt (kW) model PureCell with that of the equivalent solar and wind power systems generated a number of comments and criticism.

Looking to clarify matters and respond to readers’ comments, including adding information about the infographic’s underlying assumptions and data sources, I got back in touch with UTC Power’s marketing and communications manager Mike Glynn with the help of the MSL Group’s Mary McCeney. I believe it pays to keep an open mind when considering clean, green energy alternatives.

In the process, I learned about two high-profile applications of UTC Power’s PureCell fuel cell systems. First, 12 UTC Power PureCell Model 400 fuel cell stacks are now on site at the new World Trade Center in downtown New York City. Providing 4.8 megawatts (MW) of clean power when operational, the combined systems will rank as one of the largest fuel cell installations in the world, according to UTC.

In a second installation, solar and fuel cell power are both providing clean energy at The Octagon, a mixed-use residential and commercial building complex on Roosevelt Island in midtown Manhattan. A 50kW solar power array and a PureCell Model 400, 400kW system are supplying 50% of the building’s power needs.To read more click here...

An employee of Sony demonstrates a new bio battery, generated from the
cellilose of recycle papers, powering a fan (L) at the Eco-Products
exhibition in Tokyo. Japanese electronics giant Sony on Thursday
revealed technology that generates electricity from shredded paper. Credit: AFP

As an environmental products fair opened in Tokyo, Sony invited children to put paper into a mixture of water and enzymes, shake it up and wait for a few minutes to see the liquid become a source of electricity, powering a small fan.

"This is the same mechanism with which termites eat wood to get energy," said Chisato Kitsukawa, a public relations manager at Sony.

While academic research has previously taken place on this kind of power generation, proof-of-concept demonstrations are rare, he said.

The performance was part of Sony's drive to develop a sugar-based "bio battery" that turns glucose into power.

Shredded paper or pieces of corrugated board were used at the fair to provide cellulose, a long chain of glucose sugar found in the walls of green plants.

Enzymes are used to break the chain and the resulting sugar is then processed by another group of enzymes in a process that provides hydrogen ions and electrons.

The electrons travel through an outer circuit to generate electricity, while the hydrogen ions combine with oxygen from the air to create water.

"Bio batteries are environmentally friendly and have great potential" as they use no metals or harmful chemicals, Kitsukawa said.

But the technology is a long way from commercial viability because of its low power output. It is currently sufficient to run digital music players but not powerful enough to replace commonly used batteries, he said.

Sony first unveiled test sugar battery technology in 2007 and has since reduced the battery's size into a small sheet.Another sugar battery was on display at the fair embedded in a Christmas card, which played music when drops of fruit juice were added to it.

A designer has come up with a unique and futuristic solution for speeding up rail travel: he doesn't want to change the engines, or the tracks -- he wants to get rid of the stations.

Determined to take rail transport into the 21st century, Paul Priestman, director of British design group Priestmangoode, is the man behind the "Moving Platforms" concept, which he believes could potentially revolutionize the rail industry.

His scheme would see travelers served by a carousel of trams and high-speed trains that would take passengers from their homes to their destinations without them ever having to use a bus, car or taxi.

"The idea with Moving Platforms is that ... if you were going on holiday or on business for instance, you could get onto a tram on your street and then seamlessly travel from that onto the high-speed line and then get off at your destination in another city, then onto a tram and then end up at your destination without ever having gone in your car or perhaps got on a bus," says Priestman.

"It's totally integrated into a sort of larger transport system," he adds.

The idea is to have a city-wide network of trams that travel in a loop and connect with a high-speed rail service.

But instead of passengers having to get off the tram at a rail station and wait for the next HSR service to arrive, the moving tram would "dock" with a moving train, allowing passengers to cross between tram and train without either vehicle ever stopping.

"The trams speed up and the high-speed train slows down and they join, so they dock at high speed," explains Priestman.

"They stay docked for the same amount of time that it would stop at a station," he adds.

Credit: CNN

"There are big doors, there are wide doors, they're all the same level so you can seamlessly go between the two vehicles quite peacefully; there's no hurry.

"Then, when everyone's done that, the doors shut and then the trains separate and the tram then goes back into the city or town and picks up more passengers and drops off passengers."

Instead of using paper tickets to pass through a barrier, passengers would used an RFID (radio-frequency identification) system to transfer from tram to train. Similar systems that let passengers scan pre-paid smartcards are already used on many public transport networks.

While Priestman admits that it will be some time before his vision could be implemented, he says the time has come to rethink how we travel.

"This idea is a far-future thought but wouldn't it be brilliant to just re-evaluate and just re-think the whole process?" he says.

The SIM-LEI electric car can travel 333 kilometers on a single charge,
say its creators.

There may have been more alluring electric cars on display at this year's Tokyo Motor Show, but the beauty of this prototype lies in its performance.

The SIM-LEI can travel 333 kilometers (more than 200 miles) on a single charge, say its Japanese creators SIM Drive, and it also boasts supercar-like acceleration -- 0 to 60 mph in just 4.8 seconds.

The key to these remarkable statistics lies not, as you might expect, underneath the hood but in its wheels.

Most electric vehicles house a single motor in the area vacated by the petrol engine, but the SIM-LEI has four motors, which fit in the hubs its wheels.

Each one delivers 65 kilowatts, giving the car a total output of 260 kilowatts, compared with the 80 kilowatts of output available in, say, the Nissan Leaf.

A 24.5 kWh battery sits below the floor along with inverters and controllers, which fit into a unique steel monocoque helping reduce weight, according to SIM Drive.

The SIM-LEI -- LEI stands for Leading Efficiency In-Wheel motor -- took 15 months to complete and builds on advances made with the fantastic-looking Eliica -- a super-fast eight-wheeler designed by SIM Drive CEO and President Hiroshi Shimizu.

His latest design may not look so sporty but the SIM LEI does come with low-friction tires and a low-set chassis, which helps reduce drag, says the company.

Recent technological advances are making in-wheel motors more attractive, says James Widmer, from the Center for Advanced Electrical Drives at the UK's Newcastle University.

"Motors have become more powerful for their weight and the volume they take up, which has made it more practical to get very good performance from putting electric motors directly in the wheels of cars," Widmer said.

And electric motors provide drivers with far greater control than internal combustion engines, he says.

"If you do put an electric motor in each wheel then there are huge possibilities with things like traction control and stability control," he added.

While car makers including Peugeot and Mitsubishi have used in-wheel motors in concept cars that have never been commercially available, SIM Drive hopes its four-seat sedan will go into production in 2013.

SIM Drive says the price will depend on how many it makes, but if the car ends up being mass produced, customers can expect to pay around ¥2.5 million ($32,000).

Coat a sapphire disk with a few microns of superconducting ceramic, drop it over some magnets, and watch it float. The seeming miracle is the result of "quantum trapping." That and the hard work of some researchers at Tel Aviv University.

Levitation was once relegated to the realms of mystic texts and mountain top yogis. No longer. Thanks to researchers at Tel Aviv University, Israel, objects in our time can float comfortably in the air, gliding through it friction free or hovering as motionless as a bronze cast of Saint Joseph of Cupertino.

The objects in question are no air hockey pucks, nor are they the finicky, gyroscopic magnets of yester-decade's Levitron. We're talking superconductors--high-transition temperature superconductors.

In the video above, Dr. Boaz Almog, a researcher with Tel Aviv's High Tc Superconductivity Group, can be seen placing a small disk over a magnetic track. There it remains, in whatever orientation he leaves it, centimeters away from the magnets. It does not fly off to the side, repelled by the magnetic field, nor does it skate about willy-nilly when released. When Almog adjusts the disks attitude to a rakish angle, it stays put till touched again. When hit with a flick of a finger it glides over the magnets as if friction were a property of some other universe.

The disk hovers above the magnets. Credit: ASME

To make the magic happen, Almog and his compatriots, Professor Guy Deutscher and Mishael Azoulay, coated a sapphire disk, the thickness of a business card or two, with a few microns of yttrium barium copper oxide. This ceramic goes superconductor at a mere negative 301°F. Sounds chilly, to be sure, but it's a good 100 degrees warmer than physicists thought was the limit back in the 1980s. In fact, 301 is balmy enough that a good dose of liquid nitrogen can whip the YBCO into superconductivity.

When properly cooled, superconductors do their conducting with zero resistance. They also become averse to all magnetic fields. Usually that's a deal killer for any magnet/superconductor relationship. But thanks to the thinness of Almog's disk, a magnetic field can enter it here and there in the form of "flux tubes." Where they penetrate the disk, superconductivity is locally destroyed. The magnetic field has holes in it and the superconductivity circulates around them, pinning them, and the disk, in place. The effect is strong enough that the disk can hover five centimeters above the magnets, "a world record for levitation of superconductors," says Almog.

The phenomenon is made possible, in part, by the group's initial ignorance of how to grow a superconducting layer. They used a buffer between the YBCO and the sapphire that was thought to be inferior by other researchers. Though their buffer material is less compatible with YCBO than the more common buffer material, it allowed them to grow a thick, mechanically strong, and crack-free film. "It was pure accident," says Almog. "We had this buffer material laying in our lab and we thought, 'What the hell, let's use it.'"

The magnetic field penetrates in
the form of quantum flux tubes.

Does all this mean we'll soon be commuting to work on personal quantum levitating hovercrafts? Someday. Maybe. "In principal it would be possible to levitate very heavy objects," says Almog. "If you could stretch our technology to the edge and grow tens of microns of superconductor with a one meter surface you could have a very strong levitation—you'd have to pave your road with magnets. Will it be economical? I'm not sure."

What, then, does one do with a levitating superconductor? "I hoped that from this exposure, someone one would suggest an application," says Almog. "But it didn't happen."

Until someone thinks of something, the piece will remain a curio (one soon available for play in Lancaster, PA, at the North Museum of Science and Natural History. The museum bought one from Almog after he gave a demonstration there). Once again, we have to put our hovercraft dreams in suspension.

The brewing solar trade war between the United States and China sullies what should be a triumphant moment in the global photovoltaic (PV) industry: the arrival of affordable solar electricity.

After decades of global competition and collaboration, many solar markets around the world have reached grid parity—the point at which generating solar electricity, without subsidies, costs less than the electricity purchased from the grid. In other words, solar technology is ready to be a major contributor to solving our planet's energy and environmental crisis.

However, trade protectionism threatens to inhibit the solar industry at the very time when it is breaking through to a new level of global interdependence, collaboration, and maturity.

On October 18, the U.S. government was asked to impose tariffs on imports of Chinese solar cells and modules, based on the argument that China-based producers have been heavily subsidized and are selling solar products at unfairly low prices. Perhaps not surprisingly, some Chinese companies have now asked the Chinese government to impose tariffs on imports of American solar products, arguing that U.S.-based producers have been heavily subsidized, too. And just like that, the production of affordable and competitive solar products has become a political liability in the world's two largest producers and consumers of energy.

The success of the entire solar industry hinges on the success of not one country or one company, but global competition and collaboration, which drives efficiency improvements and cost reductions worldwide. If trade barriers are imposed in the U.S., China, or Germany, it could cause a significant increase in the price of solar products and therefore solar electricity, globally. That could cause a further erosion of political support for the solar industry at a critical juncture.

Altogether, a solar trade war could undermine decades of international innovation and stall the global adoption of advanced solar technology.To read more click here...

Friday, 16 December 2011

Climate change will increase the amount of electricity generated by solar power in some parts of the world while decreasing it in others. The University of Leeds findings, published in the journal Energy and Environmental Science, have major impacts for countries looking at what type of solar power to build, where to build it and financial rates of return.

One of the study's authors, Professor Piers Forster from the School of Earth and Environment, said: "Climate models are now good enough for making continental scale predictions of several types of change, making them an increasingly useful tool for developing adaption strategies."

The study showed that projected changes in temperature and insolation (sunlight) during 2010-2080 will affect two fast-growing solar technologies: concentrated solar power (CSP) and photovoltaics (PV).

For Europe, there were positive results for both photovoltaics and CSP outputs.

Dr Rolf Crook from the Energy and Resources Research Institute, another of the study's authors, said the relative contribution from changes in insolation and temperature to changes in solar power output depended on the location - for example, in Europe the increased output is largely caused by increased insolation.

In mainland Europe, outputs of CSP, an industry-scale solar power that uses mirrors to focus large amounts of sunlight on a small area, will increase by about 10% (5.5% in the UK).

Outputs of PV, large flat panels that convert sunlight directly into electricity, will increase in mainland Europe by about 3.5% (1.2% in the UK), the study found.

In other parts of the world, PV output will increase by a few percent in China, see little change in Algeria and Australia, and decrease by a few percent in western USA and Saudi Arabia.

CSP output will increase by several percent in China and a few percent in Algeria and Australia, and decrease by a few percent in western USA and Saudi Arabia.

Even an increase of a few percent in CSP outputs in North Africa could have substantial benefits for the two billion euro Desertec (EU-MENA) project, the world's most ambitious solar power plant, incorporating CSP, PV and wind technology across 12 sq kilometres.

Desertec aims to provide half the electricity used by Europe, the Middle East and northern Africa by 2050. Building work is due to start next year in Morocco. A similar concept has been proposed for Australia and Asia.

The study found CSP is more sensitive to climate change than PV.

Dr Crook said the findings would be significant as solar power increasingly contributed to electricity generation in a low-carbon economy.

The findings come at the same time the government withdraws subsidies for households planning to install PV solar panels.

Dr Crook said: "We have shown, perhaps surprisingly, that climate change will have a positive impact on the output of solar power plants in many parts of the world. This further strengthens the case for research and investment in solar power today. Subsidies play a vital role in driving down the cost of solar technology. Cutting subsidies would only have a negative effect."

Regions were selected for the study on account of existing or planned large PV or CSP solar power plants.

The findings are linked only to climate changes impacts; whether countries own or plan to own a large or small quantity of solar power infrastructure was included in the calculations.

The Inorganic Solid State & Materials Research Group is using nanotechnology to try to find a way of turning the universe’s most abundant element, Hydrogen, into a viable source of energy.

When hydrogen is combusted in air, it binds with oxygen to create energy alongside a solitary byproduct: water. Being a relatively cheap and very green source of power, hydrogen is an attractive proposition for companies who are keen to support research into the next generation of fuels and, as a result, the Glasgow researchers have the backing of a consortium of major companies. Indeed, EADS Innovation Works, of which Airbus is a subsidiary, are testing the technology in aeroplanes, with plans in place to build and test a hydrogen fuel cell system in an unmanned aircraft in 2014.

‘The technology that we’re working on at Glasgow is at the forefront of research into sustainable fuels,’ says Glasgow Professor of Inorganic Materials Duncan Gregory, who is head of the research group which is working on hydrogen storage and sustainable energy materials. ‘We are the only group in Scotland working in this area and we have been awarded an Engineering & Physical Sciences Research Council grant of over £3 million to work with the Universities of St Andrews, Strathclyde and Newcastle on a four-year project to develop a new hybrid system combining hydrogen storage, fuel cells and lithium batteries.

‘This is an exciting time to be working in this area, but it is very challenging work.’

Trying to store hydrogen is notoriously difficult; problems can occur in attempting to keep the substance in a manageable form useful in applications such as cars or aeroplanes. In order for hydrogen to be a feasible fuel source for a vehicle, it needs to be stored safely, occupy a relatively small volume and present a minimal burden in terms of weight. Finding a way of storing hydrogen that fulfils all these necessary requirements has so far proved so difficult that using hydrogen as a fuel might still seem a long way off.

The most feasible option is storing hydrogen as a solid; this involves binding the hydrogen atoms to another substance that would act like a sponge, soaking it up; the hydrogen could then be safely stored until it was needed. Until now the problem with this method was that existing materials either bonded to the hydrogen too strongly or not strongly enough.

To overcome this problem, the team at Glasgow are using nanotechnology to build a new substance to their own specifications, which is capable of trapping and releasing hydrogen only under the right conditions.

‘We’re approaching this by trying to develop some kind of nanomaterial that fits our purpose,’ says Professor Gregory. ‘The reason that we are doing this is that when it comes to solid-state storage there are two extremes; on the one hand you can have porous, spongelike solids that are easy to get hydrogen to bind to, but they also release it too easily; on the other hand, you can have materials that hold the hydrogen too well, meaning that you have to heat the material up to get it to release again and this requires energy.

‘So what we need is some kind of solution that’s in the middle of these two extremes and we think nanofabrication is the way to do this.’

Using the state-of-the-art synthesis techniques and facilities at the University’s Kelvin Nanocharacterisation Centre, the group can begin to build compounds to meet their needs and make the reactions that bind hydrogen to solids in a fuel cell much easier to control.

‘We have a patent on a nanostructured material, based on lithium nitride, and when you react this with hydrogen it goes through two stages whereupon hydrogen becomes bonded in the structure,’ says Professor Gregory.

‘There are several ways in which making a nanostructured version of this material improves its performance: for example, we can get reactions to happen faster because the nanomaterials have a high surface area. However, we also want to see if we can apply our techniques to create other materials that may have different and useful properties, and there are companies backing us who are interested in the work we are doing here at the University.’

Indeed, the work done by university research groups such as Glasgow’s are opening the gates to a new world of energy production. Although we are only at the research stage, the potential of this technology is huge, as harnessing the potential of hydrogen may be the beginning of the end of our reliance on fossil fuels and a step towards a cleaner and greener future.

The world’s largest plant producing high capacity lithium-ion batteries has been launched in Novosibirsk region today. The plant belongs to the LIOTECH Company – a joint venture between Russian Corporation of Nanotechnologies (RUSNANO) and the International holding Thunder Sky Limited. The total investment in the project has amounted more than 13,5 billion rubles. The plant which overall area of production facility is over 40 000 sq. m. has been built in a record-breaking period, just in 9 months.

Alexey Homlyaskiy, the Deputy Governor of Novosibirsk Region, Anatoly Chubais, the Chairman the Board of RUSNANO, Alexander Erokhin, the CEO of LIOTECH LLC took part in the ceremony of opening of a new plant.

Using ecofriendly nanostructured cathode lithium – ferrum – phosphate material (LiFePO4), the LIOTECH Plant will output batteries with different nominal capacity: 200, 300 and 700 A*hr. As of today, this material allows to achieve the best performance of the batteries within the frame of their industrial manufacturing.

The planned capacity of new plant will amount over 1 GWh or about 1 mln. batteries per year. This enables to equip with the batteries about 5, 000 electric buses annually.

The LIOTECH lithium-ion batteries differ with high-power density, do not need secondary service and have a wide temperature range of usage. These characteristics enable us to use them widely in electrical transport, as well as in power industry as energy storage devices and uninterruptible power supplies. Moreover, after batteries have been used in electric transport, they still can be utilized as accumulators in power industry during 10-15 years more. Also, it is necessary to note that recycling of such a type of accumulators is completely safe for environment.

The fact that the LIOTECH LLC has already concluded delivery contracts for batteries before the manufacturing has been launched, emphasizes being in demand of a new product. One of the main consumers of new batteries in Russia will be the MOBEL LLC; 3 billion rubles contract has already been sighed with this company.

"The new plant is a successful example of foreign high-technologies’ transfer, allowing to create a modern manufacture, in which, after reaching full production capacity over 500 people will be employed. By implementing the program of import substitution, we will create a whole cluster of new high-tech manufacturing of related materials and components as well as an Engineering Center ", - emphasizes Sergey Polikarpov, RUSNANO Managing Director.

“Implementation of public electric vehicle equipped with lithium-ion batteries of our production will significantly improve the environment situation in large cities of Russia. Utilizing of batteries together with alternative energy sources will boost the development of "green technologies" and increase the energy efficiency of the economy of the Russian Federation. Russian Railway Company and Moscow underground rapid transport system, electricity supply network and power generation companies, military industrial enterprises as well as housing and communal services, telecommunication companies have already shown a great interest towards energy storage units of our batteries”, - notes LIOTECH CEO, Alexander Erokhin.

For the first time, the chemical "fingerprints" of the element mercury have been used by University of Michigan researchers to directly link environmental pollution to a specific coal-burning power plant.

The primary source of mercury pollution in the atmosphere is coal combustion. The U-M mercury-fingerprinting technique – which has been under development for a decade – provides a tool that will enable researchers to identify specific sources of mercury pollution and determine how much of it is being deposited locally.

"We see a specific, distinct signature to the mercury that's downwind of the power plant, and we can clearly conclude that mercury from that power plant is being deposited locally," said Joel Blum, the John D. MacArthur Professor of Earth and Environmental Sciences.

Blum is co-author of a paper published online Dec. 13 in the journal Environmental Science & Technology. The lead author of the paper is U-M doctoral candidate Laura Sherman, who works with Blum.

"This allows us to directly fingerprint and track the mercury that's coming from a power plant, going into a local lake, and potentially impacting the fish that people are eating," said Sherman, who has worked on the project for four years.

Mercury is a naturally occurring element, but some 2,000 tons are emitted to the atmosphere each year from human-generated sources such as incinerators, chlorine-producing plants and coal-fired power plants.

This mercury is deposited onto land and into water, where microorganisms convert some of it to methylmercury, a highly toxic form that builds up in fish and the animals that eat them. In wildlife, exposure to methylmercury can interfere with reproduction, growth, development and behavior---and may even cause death.

Effects on humans include damage to the central nervous system, heart and immune system. The developing brains of fetuses and young children are especially vulnerable.

Among mercury researchers, there has been a long-running debate about how much mercury pollution is deposited near emissions sites and how much is lofted high into the atmosphere, where it becomes part of a global mercury reservoir comprised of emissions from countless mercury sources around the world. Some researchers have argued that there is limited local mercury deposition and that most human mercury emissions end up in the global atmospheric pool.

But results from the latest study by Sherman and her colleagues prove that mercury is deposited locally near coal-fired power plants and doesn't simply vanish into a global pool high in the sky. "It makes it hard to argue that there's no local deposition when we're seeing such unique signatures like this," Sherman said.

The mercury fingerprinting technique relies on a natural phenomenon called isotopic fractionation. All atoms of a particular element contain the same number of protons in their nuclei. However, a given element will have various forms, known as isotopes, each with a different number of neutrons in its nucleus.

Mercury has seven stable (non-radioactive) isotopes. During isotopic fractionation, different mercury isotopes react to form new compounds at slightly different rates. Sherman and her colleagues measured a type of isotopic fractionation called mass-dependent fractionation (MDF), in which the different reaction rates depend on the masses of the isotopes.

Using MDF, the researchers compared the ratio of different mercury isotopes in their samples. That ratio provides a unique chemical signature, or fingerprint, that can be used as a diagnostic tool to compare environmental samples from various locations.

The latest study involved collecting daily rainfall samples in July 2009 from four sites surrounding a coal-fired power plant in Crystal River, Fla., which is on the Gulf of Mexico coast roughly 80 miles north of Tampa. To read more click here...

The efficiency of conventional solar cells could be significantly increased, according to new research on the mechanisms of solar energy conversion led by chemist Xiaoyang Zhu at The University of Texas at Austin.

Zhu and his team have discovered that it's possible to double the number of electrons harvested from one photon of sunlight using an organic plastic semiconductor material.

"Plastic semiconductor solar cell production has great advantages, one of which is low cost," said Zhu, a professor of chemistry. "Combined with the vast capabilities for molecular design and synthesis, our discovery opens the door to an exciting new approach for solar energy conversion, leading to much higher efficiencies."

Zhu and his team published their groundbreaking discovery Dec. 16 in Science.

The maximum theoretical efficiency of the silicon solar cell in use today is approximately 31 percent, because much of the sun's energy hitting the cell is too high to be turned into usable electricity. That energy, in the form of "hot electrons," is instead lost as heat. Capturing hot electrons could potentially increase the efficiency of solar-to-electric power conversion to as high as 66 percent.

Zhu and his team previously demonstrated that those hot electrons could be captured using semiconductor nanocrystals. They published that research in Science in 2010, but Zhu says the actual implementation of a viable technology based on that research is very challenging.

"For one thing," said Zhu, "that 66 percent efficiency can only be achieved when highly focused sunlight is used, not just the raw sunlight that typically hits a solar panel. This creates problems when considering engineering a new material or device."

To circumvent that problem, Zhu and his team have found an alternative. They discovered that a photon produces a dark quantum "shadow state" from which two electrons can then be efficiently captured to generate more energy in the semiconductor pentacene.

Zhu said that exploiting that mechanism could increase solar cell efficiency to 44 percent without the need for focusing a solar beam, which would encourage more widespread use of solar technology.

The research team was spearheaded by Wai-lun Chan, a postdoctoral fellow in Zhu’s group, with the help of postdoctoral fellows Manuel Ligges, Askat Jailaubekov, Loren Kaake and Luis Miaja-Avila. The research was supported by the National Science Foundation and the Department of Energy.

The Smart Connector, a new sensor device, is installed in the connecting
units of coaxial cables to provide real-time information about primary
failure modes in radio-frequency cables. Researchers in RIT’s Kate
Gleason College of Engineering and PPC, a Syracuse-based
telecommunications connector equipment company, developed the device. Credit: Rochester Institute of Technology

Deterioration and damage to cellular telecommunications cables cost organizations and customers millions in lost revenue and services in the always-on digital economy. A new sensor device, smaller than a quarter, might alleviate some of the impact.

Researchers at Rochester Institute of Technology and PPC Corp. have developed the Smart Connector, a new sensor that once installed in the connecting units of coaxial cables can provide information about equipment damage and pinpoint the exact location through self-diagnosing technologies—some of the most advanced in the field today.

The sensor is one outcome of corporate research and development initiatives established at RIT that have grown over the past few years. The university and PPC Corp. signed a licensing agreement in June. Both parties are in the process of final testing and technology transfer, says Robert Bowman, professor of electrical and microelectronic engineering in RIT’s Kate Gleason College of Engineering.

The university demonstrated the feasibility of the technology and is working with PPC to further test the manufactured product, Bowman explains. “It’s one thing to conduct laboratory testing and demonstrate viability, it’s another thing to get it into a product. PPC worked very closely with us during this research effort, and we’ll work with them as they try to integrate this technology into their product line.”To read more click here...

Thursday, 15 December 2011

NREL scientist Keith Emery examines a Semprius solar module at the
laboratory's Outdoor Test Facility. NREL helped Semprius characterize
and test its tiny solar cells, which are the diameter of a dot made by a
ballpoint pen.Credit: Dennis Schroeder

How small can a solar cell be and still be a powerhouse? How about six hundred microns wide — about the diameter of a dot made by a ballpoint pen?
The U.S. Department of Energy's National Renewable Energy Laboratory recently validated greater than 41 percent efficiency at a concentration of 1,000 suns for tiny cells made by Semprius — one of the highest efficiencies recorded at this concentration. The energy conversion efficiency of a solar cell is the percentage of sunlight converted by the cell into electricity.

Seed money from DOE, together with the experts at the NREL-based SunShot Incubator Program, lifted Semprius from a small electronics start-up with a novel idea to a real difference-maker in the solar cell world.

Semprius' triple-junction cells are made of gallium arsenide. Low-cost lenses concentrate the sun light onto the tiny cells 1,100 times. Their tiny size means they occupy only one-one thousandth of the entire solar module area, reducing the module cost. In addition, the use of a large number of small cells helps to distribute unwanted heat over the cell's structure, so there's no need for expensive thermal management hardware such as heat fins.

Semprius engineers use the company's patented micro-transfer printing process to allow the micro-cells to be transferred from the growth substrate to a wafer. In a massive parallel process, thousands of cells are transferred simultaneously. This allows the original substrate to be used again and again, dramatically cutting costs. It also provides a way to handle very small cells.

This low-cost approach, which Semprius executives say can cut manufacturing expense by 50 percent, caught the eye of energy giant Siemens, which this year took a 16 percent stake in Semprius, as part of a $20 million investment from venture capitalists.

Sunshot Incubator Program Spurs Private Investment

NREL's state-of-the-art testing and characterization instruments scrutinize the quality and efficiency of solar cells, such as on this module made by Semprius.
Credit: NREL staff

Since 2007, DOE has invested $50 million for 35 solar start-ups to participate in the PV Incubator program — now the SunShot Incubator — at NREL. Private investment in those firms now totals more than $1.3 billion, a 25-to-1 multiple.

DOE and NREL selected Semprius to be one of their PV Incubator companies in 2010. Incubator companies get $1 million to $3 million to develop their concepts into actual working prototypes or pilot projects. And they also get the expertise of NREL scientists to help overcome obstacles and test for reliability and validity.

Transfer Printing Technology Evolves to Innovative Solar-Cell Use

Semprius' back story, though, begins at the University of Illinois where Professor John Rogers and his team developed the transfer-printing process initially intended for flexible electronics.

Soon, Rogers realized that applying the technology to a concentrated photovoltaic (CPV) design could be much more lucrative.

Semprius grows a temporary layer on the original gallium-arsenide substrate, and then grows the multi-junction solar cell structure on top of that layer. Then, after the wafer is processed, the transfer printing process is used to remove the cells from the gallium-arsenide substrate and transfer them to an interposer wafer.

"We're using a completely different approach to what has been practiced," said Kanchan Ghosal, CPV Applications Engineering Manager and the principal investigator for Semprius' PV Incubator Award. "This approach uses micro-cells and transfer printing to significantly reduce the use of materials in highly concentrated PV modules. And it provides a highly parallel method to manufacture the module, based on established microelectronics processes and equipment."

NREL's state-of-the-art
testing and characterization instruments
scrutinize the quality and efficiency of solar cells, such as on this
module made by Semprius.Credit: NREL staff

Demand for Concentrated PV Expected to Double Each Year

This solar cell module made by Semprius is being tested at NREL's Outdoor Test Facility.
Credit: NREL staff

Semprius broke ground on a manufacturing plant in Henderson, N.C., this year. The state of North Carolina and local agencies kicked in $7.9 million for the 50,000-square foot plant, which is expected to employ 256 people at full build-out.

North Carolina Gov. Bev Perdue cited her state's "investments in education and job training" as the reason the company chose to locate there. The plant is expected to start operating next year, with an initial capacity of 5 megawatts, eventually growing to 35 megawatts.

The available market for highly-concentrated photovoltaics is expected to double or more each year over the next nine years, reaching greater than 10 gigawatts of power by 2020, according to Semprius CEO Joe Carr.

Partnership with DOE and NREL Proves Fruitful

Semprius first looked at using its micro-transfer printing for solar cells in 2007, with the help of a "Next-Gen" grant from DOE's Office of Energy Efficiency and Renewable Energy.

In 2010, Semprius earned one of four spots in what is now the SunShot Incubator, which is funded by DOE and run out of NREL.

This solar cell module made by Semprius is being tested at NREL's
Outdoor Test Facility. Credit: NREL staff

Ghosal laughs when he remembers the frantic moments finishing the application for the PV Incubator.

"We barely met the criteria," Ghosal said. "The rules said that you had to have a module ready to be eligible, but we only had small squares with a couple of cells, not a real module."

So, the Semprius engineers "worked feverishly day and night to make our first module."

"Two days before the deadline, we were able to get good results from that first module," Ghosal said. "We applied for the Incubator grant with the results from this module and a scale-up plan."

When Ghosal asked the company's engineers about whether they could meet the hard deadlines and aggressive goals laid down by NREL, "I was met with a lot of apprehension," he recalled. "NREL was asking for a lot of deliverables that had not been done before."

But it all worked out, and Semprius became the latest Incubator company to achieve more than it thought it could via the strict dictates of the NREL contract.

"It looked like a tall order, but we met all our goals," Ghosal said.

Kaitlyn VanSant, NREL's technical monitor for Semprius, said the company is being too modest.

"They actually met the goals a lot faster than originally anticipated," VanSant said. "The goals were definitely aggressive, but they accomplished them quicker than the timeline."

The modules to be made in the North Carolina plant starting next year will be 24 inches by 18 inches, and about 2 and a half inches deep, have a concentration of more than 1,100 suns and an efficiency of more than 31 percent. These modules would be cost competitive with fossil fuel technology at high volume.

NREL's role was critical, Ghosal said.

"A lot of the early benefits were from the testing NREL could do. NREL has an internationally recognized testing program," Ghosal said. "It's one thing to claim a particular output, but something different to say that it was validated at NREL. It gives that stamp of credibility.

"Also, we learned from NREL how vigorous we had to be in terms of the materials we are using," Ghosal said. "We got an understanding of how it would perform in the field and got some important pointers of what to watch for."

Queensland University of Technology PhD student Wesam Al Sabban is a genius and has the medal to prove it!

The engineering student received the accolade for his work on the design of an unmanned aerial vehicle (UAV) that would be powered by the sun and wind.

"While all aeroplanes mimic the shape of birds, the Green Falcon II will literally use the wind to power its movement, just as a bird would," Mr Al Sabban said.

"As part of my PhD topic we are studying the way birds make use of wind energy to fly with minimum power, the way they glide and use all types of wind to move and change their flight path.

"We're developing a UAV with artificial intelligence to forecast solar intensity and use wind patterns for path planning and to power the UAV.

"Quite frankly, we expect it to fly like the wind and because it will run on solar and wind power it'll be cheaper to operate than similar sized UAVs on the market."

While a final design is about eighteen months away, Mr Al Sabban was presented with a trio of awards at the recent 63rd iENA International Trade Fair, a mega inventors' showcase held each year in Nuremberg, Germany.

He was awarded an independent inventor iENA Gold Medal, a certificate from the International Federation of Inventors Association (IFIA) for outstanding achievement in a world competition for green inventions and was awarded an honorary Genius Prize from the Association of Hungarian Inventors (MAFE) - the only Genius Prize awarded this year.

At the trade fair, Mr Al Sabban's invention competed with more than 750 others from 30 countries.

Other notable products to come out of previous trade fairs include the skateboard, suitcase on wheels and a folding bicycle.

"We're very interested in green technology and for a number of years we have been working on a UAV to mimic the way birds fly so Wesam's success is a fabulous result," said his PhD supervisor at QUT Dr Felipe Gonzalez.

Dr Gonzalez, a QUT Aerospace Avionics lecturer based at the Australian Research Centre for Aerospace Automation (ARCAA) said the awards illustrated the world-class research of QUT in artificial intelligence, unmanned systems for civilian applications and aerospace avionics.

"The Green Falcon II will be a zero-emissions UAV capable of round-the-clock service," he said.

"The iENA awards prove there is a market for efficient UAV development and we'll be looking for partners to turn this unique UAV design into a commercial reality by 2013."

Mr Al Sabban, a Saudi Arabian engineer, moved to Queensland in 2007 to further his engineering education. He was sponsored by the Government of Saudi Arabia as well as ARCAA to present his Green Falcon II at the iENA trade fair.

Danish researchers believe they have a breakthrough in tidal power, using the waves of the ocean to generate energy.

Weptos is a small power plant which lies on the ocean, tied to the ocean bed. The waves move flaps on the two arms of the device which spin an axel, which then generates the power.

Each machine is a separate unit, so they are very easy to move around, adjust and fix.

Each devise also moves its two arms as the weather conditions change. In severe weathers it narrows meaning it is more stable and does not lose its energy-making capabilities.

The device is also scalable, which means the bigger the unit, the more energy, up to a certain degree of course.

In total over 200 tests has looked "exceedingly promising," according to the developers.

"I think this unit has a very good chance of making a breakthrough in this field," says Jens Peter Kofoed, an associate professor at Aalborg University's Department of Civil Engineering, where Weptos is being developed.

Previous attempts to make profitable wave power plants have faltered because they have not met the three vital parameters: the ability to turn waves into electricity, a robust construction to withstand the impact of powerful waves, and relatively low construction and maintenance costs.

The next version will be 10-15 size the prototype, which is only a medium sized one to the envisaged final version.

Optics and photonics may one day revolutionize computer technology with the promise of light-speed calculations. Storing light as memory, however, requires devices known as microresonators, an emerging technology that cannot yet meet the demands of computing. The solution, described in a paper published today in the Optical Society's (OSA) journal Optics Letters, may lie in combining light's eerie quantum properties with a previously unknown quality of optical fiber.

Researchers from OFS Laboratories in Somerset, N.J., have developed a precise and efficient way to create microresonators by making nanoscale changes to the diameter of normal optical fiber. These narrow sections are able to confine light, sending it on a back-and-forth corkscrew path inside a length of optical fiber and creating a microresonator.

Though trapping light in this so-called "Whispering Gallery" mode is a well-known phenomenon, the researchers have discovered a quick, efficient, and accurate way to manufacture long chains of these new microresonators, all based on a never-before-recognized characteristic of optical fiber. This is a new technology path and an essential step toward designing a practical optical computer, as described in the Optics Letters paper.

"Optical computers, which use light particles—photons—in place of electrons to process and store information, have the potential to be much faster than today's electronic computers," said Misha Sumetsky, a researcher at OFS Laboratories and lead author on the study. "Unfortunately, manufacturing microresonators that meet the demands of optical computing has been a long and, until now, unsuccessful pursuit."

Designing a practical microresonator has been something of a "Holy Grail" on the path to optical computers. The current microresonator manufacturing technology is based on the well-established process of silicon lithography, which etches extremely precise features onto silicon wafers. For microresonators the most promising design appeared to be a long series of microscopic loops, which bottle up photons in whirling circles and then pass them from one ring to the next. The longer the chain, the longer the signal could be stored as memory. Unfortunately, even the most precise manufacturing processes still produce tiny imperfections in the rings. These bumps on the road slowly weaken the signal, attenuating the light, and allowing the memory held in the buffer to fade away.

Sumetsky and his colleagues at OFS Laboratories, formerly part of the famous Bell Labs, pursued a path that abandoned the silicon wafer in favor of the silica strand of optical fiber.

In conventional applications, optical fiber—a very pure form of glass—uses the fundamental properties of light and refraction to keep light from slipping out and diffusing. The core and cladding of optical fiber have slightly different indexes of refraction, giving the fiber the ability to bend the path of light without causing scattering. Light traveling through the fiber bounces back and forth inside the core, keeping it traveling along the fiber for many kilometers with very little signal loss.

Coaxing Light into a Whispering Gallery

This sends the light careening through the fiber at extremely high speed, but just as cars barreling down the highway sometimes get directed onto "cloverleaf" off ramps, so too can light be coaxed from the fiber and into a spiral path. Unlike cars, however, light doesn't need to slow down on the off ramp.

In this case, the off ramp is created by narrowing the fiber to a small diameter to coax the light out of the core and into a fiber aligned perpendicularly and positioned very close to, or actually touching the first. Because they are so close, and the original fiber narrows down to a mere fraction of its original size, a portion of the light is able to make a literal "quantum leap" to the other fiber. This is an effect known as "evanescent coupling" and it enables an electromagnetic wave – light – to connect (or couple) from one fiber to another.

The light now finds itself not traveling down a straight path but rather racing around the fiber surface in very tight circles. Even though the light maintains its original pace within the glass, because it's really taking the long way around, corkscrewing along the new fiber's surface, it propagates down the fiber at a fraction of its original speed (figure 1).

This special redirection of light is known as the "Whispering Gallery" effect, named after the phenomenon that takes place in certain architectures, such as the St. Paul's Cathedral in London and Grand Central Station in New York, where someone whispering along the wall would hear their whisper coming from behind them as the sound traveled around the edge of the room and returned to its original spot (figure 2).

Optical Fiber Microresonators

Sumetsky and his colleagues were able to vary the optical fiber diameter by several nanometers. They did this with unprecedented precision, on the order of a hundredth of a nanometer.

This dimpling or narrowing of the fiber effectively changes the properties of the Whispering Gallery and has the effect that light traveling along the surface of the fiber would turn around and head back the way it came. If it were traveling between two of these narrowed portions of fiber, the light would continue to resonate back and forth with very little loss of signal. This is, in fact, the microresonator.

These optical fiber microresonators currently are able to retain light two orders of magnitude longer than lithographic microresonators – and the researchers say it's possible to push that number even higher.
If sufficient number of optical fiber microresonators were coupled together, again taking advantage of evanescent coupling, then any information contained in the light pulses could be stored long enough for computational purposes. The researchers have so far been able to couple 10 optical fiber microresonators, an important proof-of-concept step.

Manufacturing is a ‘SNAP'

It's possible to create these nanoscale changes to the radius of the fiber by exploiting a property inherent in the fiber created during manufacturing and discovered at OFS Laboratories several years ago. Optical fiber is made by heating a much thicker rod of glass with a precise chemical makeup and stretching and drawing it out into extremely fine and flexible fibers. When the fiber is drawn out, the process introduces certain tension, and this tension is frozen in, creating a predetermined amount of stress.

The researchers harnessed this fixed stress by directing a laser beam at the fiber to heat it. By raising the fiber's temperature, but keeping it well below the melting point, it was possible to release this intrinsic pressure, changing the diameter and refractive index of the fiber without deforming it any further. As long as the fiber is produced under the same conditions and it is heated below the melting point, the same effect is always achieved. This process enables a technology that the researchers call Surface Nanoscale Axial Photonics (SNAP).

"We heated it to a temperature lower than the melting temperature," said Sumetsky. "This annealing allows us to change the radius in this nanoscale range. In the new system, the accuracy of the fiber radius variation is about 0.1 angstrom – orders of magnitude better than achieved before."

Previous attempts have been made at harnessing optical fiber for microresonators, but these relied on polishing or melting the fiber to change its diameter. This produced very uneven results and could not achieve nanoscale dimensions. To enable evanescent coupling, it's vital that the circumference of the microresonators be controlled to sub-angstrom accuracy. The SNAP process ensures this accuracy and that each microresonator is nearly identical.

This is the crucial point the researchers believe will enable the technology to move from laboratory studies to manufacturing. As long as the optical fiber is produced under the same conditions, it will always produce the same effect when heated, changing its properties in the same precise manner. "We can faithfully reproduce these resonators. There's a real, robust way of fabricating these, and this is the first paper that actually shows that," Sumetsky said.

According to the researchers, it's possible these microresonators could be used in specialized devices in about two to three years. However, their greatest potential may be in pioneering optical computing and in enabling fundamental physics research.

The green building industry, concern over global warming, and the rising cost of fossil fuels have driven recent interest in renewable energy, making relevant products and systems more readily available and easier to use. Unlike finite energy sources like fossil fuels, renewable sources like solar, wind, biogas, biomass, and geothermal are for the most part inexhaustible, provided they are used at the rate at which they are naturally replenished.

As the renewable energy industry has grown, a new submarket has developed: the buying and selling of green power. Green power can be purchased and sold in different ways. Depending on the state, local electric utilities may offer green power options directly from its grid. Some areas even allow the buyer to choose from competitive suppliers. Renewable energy certificates (RECs), which represent a unit of renewable energy equal to 1 MWh, may be an option as well.

Sources of renewable energy currently being used in building construction projects include solar thermal, solar photovoltaic (PV), wind, biogas, biomass, and geothermal. Solar PV and wind turbines will be considered in this article. Generating green power with PV

Energy from the sun strikes the earth’s surface with an average power density of about 1,000 W/sq meter. PV modules convert the sun’s energy directly to electrical energy through the photoelectric effect. When photons strike materials like silicon, they are absorbed, causing the material to release electrons. Conducting material collects the electrons, resulting in a small electric current, which is magnified to a more usable level by connecting the solar cells in a series-parallel arrangement. The highest performing commercially available PV modules convert the sun’s energy to electricity with an efficiency of around 20%. The most common PV systems are the ground array and the building integrated PV (BIPV).

A ground array is exactly what it sounds like: an array of PV modules installed on a structure independent from a building. For construction projects with available real estate, PV arrays can be installed on the ground, any flat surface, or a hillside, and even elevated to provide shade as in the case of a parking lot carport.

BIPV uses arrays installed as an element of a building (see Figure 1). BIPV arrays can be incorporated into building rooftops and walls or installed as shading devices like window awnings. Glass surfaces can also serve as BIPV sources through the use of PV glass (see “Exelon Pavilions, Chicago”).

Commercially available PV modules include mono-crystalline silicon, poly-crystalline silicon, and amorphous (thin film) technology with conversion efficiencies of approximately 6% to 19% with a power density as high as approximately 13 W/sq ft. Mono-crystalline cells are black and are usually more efficient than blue-tinted poly-crystalline cells. Costs for both PV module types of typical efficiency are around $4/W, not including installation or incentives.

The dc produced by PV modules is converted to ac by an inverter. Inverters range in size from small models capable of serving one PV module up to large 3-phase units with ratings higher than 800 kVA. The inverter converts the dc input power to ac matching the voltage, phase, and frequency of the electrical distribution system to which it is connected. The inverter also incorporates the system controls and safety features required to shut down the PV system in the event of a grid failure or building distribution system failure. Inverters used in the U.S. are designed and tested to the requirements of UL Standard 1741 and IEEE Standard 929. PV system dc voltages are limited to 600 V in the U.S. while voltages up to 1,000 V are common outside the U.S.

Power generated by the PV system is generally consumed by the facility to which it is connected. However, instances can arise where power generated by the PV system cannot be used by the facility. In this case, power is typically allowed to flow from the PV system to the utility’s electrical grid. For this reason, net metering is required, which has the ability to measure and record power flow in either direction (incoming or outgoing).

Local regulations dictate pricing for the power purchased and sold. Pricing varies widely between countries, regions, and states, greatly affecting the economics of PV systems. To read more click here...

A pair of boron nanoribbons stuck together on a microdevice used to
measure thermal conductivity. (Courtesy of the Li Lab)

The surprising discovery of a new way to tune and enhance thermal conductivity – a basic property generally considered to be fixed for a given material – gives engineers a new tool for managing thermal effects in smart phones and computers, lasers and a number of other powered devices.

The finding was made by a group of engineers headed by Deyu Li, associate professor of mechanical engineering at Vanderbilt University, and published online in the journal Nature Nanotechnology on Dec. 11.

Li and his collaborators discovered that the thermal conductivity of a pair of thin strips of material called boron nanoribbons can be enhanced by up to 45 percent depending on the process that they used to stick the two ribbons together. Although the research was conducted with boron nanoribbons, the results are generally applicable to other thin film materials.

An entirely new way to control thermal effects
“This points at an entirely new way to control thermal effects that is likely to have a significant impact in microelectronics on the design of smart phones and computers, in optoelectronics on the design of lasers and LEDs, and in a number of other fields,” said Greg Walker, associate professor of mechanical engineering at Vanderbilt and an expert in thermal transport who was not directly involved in the research.

According to Li, the force that holds the two nanoribbons together is a weak electrostatic attraction called the van der Waals force. (This is the same force that allows the gecko to walk up walls.)

“Traditionally, it is widely believed that the phonons that carry heat are scattered at van der Waals interfaces, which makes the ribbon bundles’ thermal conductivity the same as that of each ribbon. What we discovered is in sharp contrast to this classical view. We show that phonons can cross these interfaces without being scattered, which significantly enhances the thermal conductivity,” said Li. In addition, the researchers found that they could control the thermal conductivity between a high and a low value by treating the interface of the nanoribbon pairs with different solutions.

The enhancement is completely reversible
One of the remarkable aspects of the effect Li discovered is that it is reversible. For example, when the researchers wetted the interface of a pair of nanoribbons with isopropyl alcohol, pressed them together and let them dry, the thermal conductivity was the same as that of a single nanoribbon. However, when they wetted them with pure alcohol and let them dry, the thermal conductivity was enhanced. Then, when they wetted them with isopropyl alcohol again, the thermal conductivity dropped back to the original low value.

Keeping integrated chips that contain billions of transistors, like the
one pictured, from overheating has become a major challenge for the
semiconductor industry. (Travelin’ Librarian/Flickr)

“It is very difficult to tune a fundamental materials property such as thermal conductivity and the demonstrated tunable thermal conductivity makes the research especially interesting,” Walker said.

One of the first areas where this new knowledge is likely to be applied is in thermal management of microelectronic devices like computer chips. Today, billions to trillions of transistors are jammed into chips the size of a fingernail. These chips generate so much heat that one of the major factors in their design is to prevent overheating. In fact, heat management is one of the major reasons behind today’s multi-core processor designs.

Discovery may improve design of nanocomposites
Another area where the finding will be important is in the design of “nanocomposites” – materials made by embedding nanostructure additives such as carbon nanotubes to a host material such as various polymers – that are being developed for use in flexible electronic devices, structural materials for aerospace vehicles and a variety of other applications.

Collaborators on the study were post-doctoral research associate Juekan Yang, graduate students Yang Yang and Scott Waltermire from Vanderbilt; graduate students Xiaoxia Wu and Youfei Jiang, post-doctoral research associate Timothy Gutu, research assistant professor Haitao Zhang, and Associate Professor Terry T. Xu from the University of North Carolina; Professor Yunfei Chen from the Southeast University in China; Alfred A. Zinn from Lockheed Martin Space Systems Company; and Ravi Prasher from the U.S. Department of Energy.

Through computer simulations, UB researchers found that "green routing"
can help drivers reduce fuel consumption without significantly
increasing travel time. Credit: University at Buffalo

The path of least emissions may not always be the fastest way to drive somewhere. But according to new research from the University at Buffalo, it's possible for drivers to cut their tailpipe emissions without significantly slowing travel time.

In detailed, computer simulations of traffic in Upstate New York's Buffalo Niagara region, UB researchers Adel Sadek and Liya Guo found that green routing could reduce overall emissions of carbon monoxide by 27 percent for area drivers, while increasing the length of trips by an average of just 11 percent.

In many cases, simple changes yielded great gains.

Funneling cars along surface streets instead of freeways helped to limit fuel consumption, for instance. Intelligently targeting travelers was another strategy that worked: Rerouting just one fifth of drivers -- those who would benefit most from a new path -- reduced regional emissions by about 20 percent.

Sadek, a transportation systems expert, says one reason green routing is appealing is because it's a strategy that consumers and transportation agencies could start using today.

"We're not talking about replacing all vehicles with hybrid cars or transforming to a hydrogen-fuel economy -- that would take time to implement," said Sadek, an associate professor of civil, structural and environmental engineering. "But this idea, green routing, we could implement it now."

In the near future, GPS navigation systems and online maps could play an important role in promoting green routing, Sadek said. Specifically, these systems and programs could use transportation research to give drivers the option to choose an environmentally friendly route instead of the shortest route.

Sadek and Guo, a PhD candidate, presented their research on green routing at the 18th World Congress on Intelligent Transportation Systems in October.

In the UB study on green routing, the researchers tied together two computer models commonly known as "MOVES" and "TRANSIMS."

The Motor Vehicle Emission Simulator (MOVES), created by the Environmental Protection Agency, estimates emissions. The Transportation Analysis and Simulation System (TRANSIMS) simulates traffic in great detail, taking into account information including the location and pattern of signals; the grade of the road; and the trips people take at different times of day.

After incorporating Buffalo-specific data into TRANSIMS, Sadek and Guo ran a number of simulations, rerouting travelers in new ways each time.

After running the models numerous times, the researchers reached a "green-user equilibrium" -- a traffic pattern where all drivers are traveling along optimal routes. With the system in equilibrium, moving a commuter from one path to another would increase a user's overall emissions by creating more congestion or sparking another problem.

The simulations were part of a broader study Sadek is conducting on evaluating the likely environmental benefits of green routing in the region. His project is one of seven that the U.S. Department of Transportation has funded through a Broad Agency Announcement that aims to leverage intelligent transportation systems to reduce the environmental impact of transportation.